A comparative study of Utrecht interstitial applicator and ring interstitial applicator in three-dimensional conformal brachytherapy for cervical cancer

Abstract

Objective To investigate the dosimetric differences between Utrecht applicator and ring applicator in three-dimensional (3D) conformal brachytherapy for locally advanced cervical cancer. Methods Twenty-five patients with locally advanced cervical cancer were treated with magnetic resonance imaging-guided 3D conformal brachytherapy. Utrecht applicator and ring applicator were used interchangeably for 96 cycles. Patients were divided into two groups according to the type of applicator. Each group received 48 cycles of treatment, in which ring applicator was first applied for 26 cycles and Utrecht applicator was first applied for 22 cycles. High-risk clinical target volume (HR-CTV), width, thickness, and D90 at the point A level, D2 cm3 of organs at risk (OARs), V7 Gy , W7 Gy, A, V7 Gy , A, and W/T7 Gy were evaluated and analyzed using paired t-test. Results There were no significant differences in HR-CTV and the width, thickness, and D90 at the point A level between the Utrecht group and the ring group (P=0.487; P=0.340; P=0.857; P=0.921); there were no significant differences in D2 cm3 values of bladder, rectum, sigmoid, and bowel between the two groups (P=0.136; P=0.802; P=0.985; P=0.458); there were no significant differences in V7 Gy and T7 Gy, A between the two groups (P=0.076; P=0.435). The Utrecht group had a significantly larger W/T7 Gy, A than the ring group (P=0.002). Conclusions Utrecht applicator is appropriate for patients with relatively large width and width/thickness ratio of HR-CTV at the point A level. Key words: Cervical neoplasms/Brachytherapy; Brachytherapy, three-dimensional conformal; Utrecht Interstitial Fletcher Applicator; Interstitial Ring Applicator; Dosimetry